Electrostatic generator

ABSTRACT

An electrostatic generator comprises a pair of side by side disposed endless chains, each chain comprising metal pellets insulated from one another, with metal strips interconnecting the pellets of one chain with oppositely-disposed pellets of the other chain. Induction electrodes are provided for charging the pellets and strips as the chains are made to rotate together, and for transferring the charges to a high voltage terminal.

United States Patent Allen et al. June 10, 1975 ELECTROSTATIC GENERATOR[75] Inventors: William Douglas Allen, Quirang [56] References C'tedBurcot, near Abingdon; Michael UNITED STATES PATENTS Morris, Fro both ofEngland 3,048,720 8/1962 Cloud 310/5 Assigneez United Kingdom Atomic gy3,469,118 9/1969 Herb et al 310/6 Authority London England PrimaryExaminerDonovan F. Duggan [22] Filed: Feb- 28, 1974 Attorney, Agent, orFirm-Larson, Taylor & Hinds 21 Appl. No.2 446,954

[57] ABSTRACT Relted Apphcanon Data An electrostatic generator comprisesa pair of side by [63] Commuauo of 2971838 Oct 16, 1972, side disposedendless chains, each chain comprising abandonedmetal pellets insulatedfrom one another, with metal strips interconnecting the pellets of onechain with [30] Fore'gn Data oppositely-disposed pellets of the otherchain.

Oct. 28, 1971 Umted Kmgdom 50287/71 Induction eectrodes are provided forg g the pellets and strips as the chains are made to rotate together,and for transferring the Charges to a g 58 Field of Search 310/5, 6, 7;322/2; Mtage termmal' 317/2 5 4 Claims, 3 Drawing Figures PATENTEDJUN 10 I975 SHEET ELECTROSTATIC GENERATOR This is a continuation ofapplication Ser. No. 297,838 filed Oct. I6, 1972, now abandoned.

This invention relates to electrostatic generators.

In the Van de Graff type of electrostatic generator electrical chargesare conveyed to a high voltage terminal by way of a rapidly movingendless belt of insulating material. The charges are sprayed at earthpotential from sharp corona points and collected at high potential fromother corona points.

This arrangement has several disadvantages however. For example, thearrangement results in the formation of belt dust, the formation ofcorrosive products from the corona discharges and, in particular. itresults in a tendency for surge propagation along the belt.

An improved method of conveying electrical charges to a high voltageterminal has been proposed by R. G. Herb et al. (See British PatentSpecification No. 1,254,878 and corresponding US. Pat. No. 3,469,l l8Here an endless chain of cylindrical metal pellets insulated from eachother is provided. The chain is supported by and runs between a pair ofelectro conductive pulleys and the pellets of the chain are charged byinduction. For example, that pulley remote from the high voltageterminal is maintained at earth potential and as each pellet is about toleave that pulley it enters a high voltage field imposed by an inductionelectrode adjacent the pulley and at a high negative voltage relative toit. This electrode induces a positive charge on the pellet, which chargeis conveyed to the high voltage terminal via the other pulley and adischarge electrode adjacent thereto. The Herb et a1 method offersseveral advantages over Van de Graff-type generators. For example, theHerb et al method offers freedom from the effects of corona, from beltdust and, in particular, from surge breakdown, since the breakdowntravels by way of the metal beads. However, its one significantlimitation is that its current carrying capacity is limited to currentsof approximately 100 micro amperes.

On the other hand, an electrostatic generator according to the presentinvention is believed to be capable of carrying currents which aresubstantially more than 100 micro amperes.

According to the present invention, an electrostatic generator comprisesa high voltage terminal, a pair of side by side disposed endless chainswith their bights rotatable about common axes, each of said chains beingformed by a plurality of electrically conductive pellets insulated fromeach other, laterally disposed electrically conductive membersinterconnecting the pellets of one chain with the pellets of the otherchain, means for rotating the chains, means for charging the pellets andthe members as the chains rotate and means for transferring the chargesto the high voltage terminal.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying diagrammatic drawings, wherein:

FIG. 1 is a side view of an electrostatic generator,

FIG. 2 is a section, to an enlarged scale, taken on the lines I] ll ofFIG. 1, and FIG. 3 is a side view of a modified form of generator.

With reference to FIGS. 1 and 2, a high voltage electrostatic generator1 forming part of a particle accelerator comprises a high voltageterminal 2, and a pair of side by side disposed endless chains 3 withtheir bights rotatable about common axes provided by shafts 4, 5.

i on the other pulley 13 is pulled around by the lateral i Each chain 3is formed by a plurality of electrically conductive pellets 6 insulatedfrom each other by nylon links 7. Laterally disposed electricallyconductive members 8 interconnect the pellets 6 of one chain 3 with thepellets of the other chain 3 by interconnecting oppositely facingpellets 6 of the chains 3. The chains 3 are rotated by an electricaldrive unit 9. Charging means 10 are provided for charging the pellets 6as the chains 3 rotate, and discharging means 11 are provided fortransferring the charges to the high voltage terminal 2.

In further detail, the generator 1 is housed in a pressure vessel 12filled with a high density insulating gas,

Each chain 3 is identical. The pellets 6 are of stainless steel and thelateral members 8 are of aluminium. The chains 3 are each supported byand run between grooved metal pulleys l3, 14. The electrical drive unit9 rotates one ofthe pulleys l3 and the chain 3 mounted members 8. Thusone chain 3 drives the other.

The pellets 6 are of tubular form and the lateral members 8 comprisestrips of aluminum. A pair of vertically spaced lateral members 8interconnect each oppositely facing pair of pellets 6. ln plan view thechains 3 and the lateral members 8 therebetween have a ladder-like form.

The chains 3 and lateral members 8 run through apertures formed in ahorizontally disposed insulator stack" 15 comprising glass insulatorplates 16 sandwiched between metal shielding plates 17. The insulatorstack 15 is used to support the high voltage terminal 2 within and toinsulate it from the pressure vessel 12.

The charging means 10 comprise upper and lower induction electrodes 20,21, disposed above and below the pairs of lateral members 8 and in closeproximity to the pulleys 13. A power supply 22 is used to apply anegative voltage between the cooperating pairs of induction electrodes20, 21 and the pulleys 13, which pulleys are earthed through theircommon shaft 4. The surfaces of the electrodes 20, 21 adjacent thepellets 6 and members 8 are made smooth so as to substantially eliminatesparking. Similarly, the surfaces of the pellets 6 and members 8 arerendered smooth.

The discharging means 11 comprises a pair of cooperating inductionelectrodes identical in form to the electrodes 20, 21 and theseelectrodes are also disposed in close proximity to the pulleys 5. Thecommon shaft 5 of the pulleys 5 is electrically connected to the highvoltage terminal 2 by a conductor 23 and the discharging means 11 isnegatively charged, relative to the terminal 2.

The charging and discharging means 10, 11 are disposed so that the upperruns of the chains 3 pass between their cooperating electrodes. Similarcooperating pairs of electrodes, shown at 24 and 25, are disposed sothat the lower runs of the chains 3 pass between them. The electrodes 24are disposed in close proximity to the pulleys l3 and the electrodes 25are disposed in close proximity to the pulleys 14. A power supply 26 isused to apply a positive voltage between the electrodes 24 and thepulleys 13. The electrodes 25 are positively charged, relative to thehigh voltage terminal 2.

One way of charging the means 11 negatively, and the electrodes 25positively, both relative to the high voltage terminal 2, is disclosedin either of the aforementioned British Patent Specification No.1,254,878

3 or corresponding US. Pat. No. 3,469,l l8 (Herb et al). (Seeparticularly FIG. 8 of that specification).

In operation, the drive unit 9 is used to rotate the assembly of chains3 and lateral members 8 around the pulleys l3, l4 and in the directionshown by the arrow adjacent pulley 13.

The charging means 10 serve to draw positive charges in a smooth mannerinto the pellets 6 and interconnecting lateral members 8 before theybreak contact with the pulleys 13. These charges are bound on thepellets 6 and members 8 before they break contact with the pulleys 13 sothat there is no substantial sparking on termination of contact.

As the positively charged pellets 6 and members 8 enter the negativelycharged discharging means 11 the former give up their charges which passto the high voltage terminal 2, by way of the pulleys 14, where thecharges accumulate on the surface of the terminal 2. Again, thearrangement is such that the charges flow smoothly from the pellets 6and members 8, with no substantial sparking.

As the pellets 6 and members 8 leave the pulleys 14, negative chargesare bound on them by means of the electrodes 25. They then move along topass between the electrodes 24 where a positive voltage binds thenegative charges on the pellets 6 and members 8 until after they contactthe pulleys 13. Thus sparking is substantially eliminated.

The pellets 6 and members 8 then pass around the peripheries of thepulleys 13 to be recharged and the above-described cycle is repeated.

The invention is believed to provide an electrostatic generator ofincreased current-carrying capacity, which current can be measured inmilliamperes, rather than I microamperes or so.

This is because the areas of the pellets 6 and lateral members 8therebetween are considerably greater than the pellets per se. Thus, thecurrent carrying capacity of generators according to the invention maybe greater by a factor of at least compared with the capacity ofgenerators using pellets only.

Furthermore, compared with arrangements using only endless chains ofpellets and not lateral members therebetween as well, vibration inplanes parallel to the axes of the pulleys is substantially reduced andvibration normal to the planes should be effectively damped by the denseinsulating gas in the pressure vessel 12. In addition, as twisting ofthe chains 2 is substantially re duced, wear on the insulating links isreduced correspondingly.

FIG. 3 illustrates a modification, rather similar to socalled tandemaccelerator systems, wherein double charging is employed.

In FIG. 3, the generator 1a uses first and second charging means 10a and10b. The positive charges on the pellets 6 and lateral members 8 (thelatter are not shown in this figure) are given up to a central highvoltage terminal 2a, by way of pulleys 14a and conductors 23a. Theterminal 2a is disposed between and is supported by insulator stackportions 15a, 15!). First and second discharging and sign-reversingmeans, identical to the electrodes 11, 25 ofFIG. l are not shown in FIG.3 for the sake of clarity. However, it will be understood that suchmeans are in fact disposed adjacent the pulleys 14a. 7

In FIG. 3, the bights of the chains 3 are supported by two pulleys 13,each of which is earthed. Thus in operation, the pellets 6 and lateralmembers 8 receive positive charges at the charging means 10 and thesecharges are then given up to the high voltage terminal 2a via the upperpulley 14a. The pellets 6 and lateral members 8 receive negativechargesas they leave the upper pulley 14a, which charges are bound onthem by the electrodes 24b. They are then recharged positively by thecharging means 10b.

They then give up their charges once again to the high voltage terminal2a, but this time by way of the lower pulley 14a. As they leave thispulley they receive negative charges, which charges are bound on them bythe electrodes 24a. The cycle is then repeated.

Thus, the current-carrying capacity of the generator la of FIG. 3 istwice that of the generator 1 of FIGS. 1 and 2.

We claim:

I. For electrically charging a high voltage terminal, the combinationcomprising a series of electrically conducting members of elongated formhaving smooth uncovered external surfaces, mechanical linkagesinterconnecting and electrically insulating adjacent members from oneanother thereby to arrange the members in substantially parallelside-by-side array in an endless chain, a charging station anddischarging station of which at least the former comprises inductionelectrode means disposed on both sides of the elongated members, thedischarging station being arranged for the transfer of charge from themembers to the high voltage terminal, and means for driving the endlesschain along a path of travel from the charging station to thedischarging station.

2. The combination as claimed in claim I, wherein the mechanicallinkages interconnecting adjacent elongated members comprise link meansspaced apart transversely of the path of travel.

3. The combination as claimed in claim 2, wherein the link meanscomprises a laterally spaced pair of endless chain structures each ofwhich is formed by a plurality of electrically conductive bodiesconnected to each other by links of insulating material, each saidelongated member being attached to and extending between oneelectrically conductive body of one said chain structure and onoppositely disposed electrically conductive body of the other chainstructure.

4. The combination as claimed in claim 3, provided with spaced pairs ofpulleys, the said chain structures moving around the said spaced pairsof pulleys which are electrically conducting for carrying electricalcharge to or from a said charging station or discharging station.

P511050 UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION PatentNo. 3,889,138 Dated June 10, 1975 Inventor(s) ALLEN ET AL It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

The Assignee appearing in the heading of the patent should be ScienceResearch Council, State House, High Holborn, London Signed and Scaledthis seventeenth D 3) Of February 1976 [SEAL] Attest:

RUTH- C. MASON C. MARSHALL DANN Al sllllg ()jfl've Commissioner ofParents and Trademarks P611050 UNITED STATES PATENT OFFICE 569CERTIFICATE OF CORREC Patent No. 3'889'l38 Dated une 1 975 Inventor(sLEN ET AL It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

The Assignee appearing in the heading of the patent should be ScienceResearch Council, State House, High Holborn, London Signed and Sealedthis seventeenth D3) of February 1976 [SEAL] Attest:

' RUTH c. M ssoN c. MARSHALL DANN Arresting Officer v CommissionerufPatenls and Trademarks

1. For electrically charging a high voltage terminal, the combinationcomprising a series of electrically conducting members of elongated formhaving smooth uncovered external surfaces, mechanical linkagesinterconnecting and electrically insulating adjacent members from oneanother thereby to arrange the members in substantially parallelside-by-side array in an endless chain, a charging station anddischarging station of which at least the former comprises inductionelectrode means disposed on both sides of the elongated members, thedischarging station being arranged for the transfer of charge from themembers to the high voltage terminal, and means for driving the endlesschain along a path of travel from the charging station to thedischarging station.
 2. The combination as claimed in claim 1, whereinthe mechanical linkages interconnecting adjacent elongated memberscomprise link means spaced apart transversely of the path of travel. 3.The combination as claimed in claim 2, wherein the link means comprisesa laterally spaced pair of endless chain structures each of which isformed by a plurality of electrically conductive bodies connected toeach other by links of insulating material, each said elongated memberbeing attached to and extending between one electrically conductive bodyof one said chain structure and on oppositely disposed electricallyconductive body of the other chain structure.
 4. The combination asclaimed in claim 3, provided with spaced pairs of pulleys, the saidchain structures moving around the said spaced pairs of pulleys whichare electrically conducting for carrying electrical charge to or from asaid charging station or discharging station.